U.S. Pat. No. 5,164,014 discloses the preparation of a directly-compressible starch for use in the manufacture of tablets by a multi-step process. First, a starch paste is produced by slurrying native starch in water and heating the dispersion to about 85° C. Next, the starch paste is sprayed onto native starch during a granulation process. Finally, the resulting mixture is dried, ground and sieved to obtain granules having a mean particle size of 100 to 500 micrometers (a.k.a. microns). The amount of starch paste is 1–20% by weight of the binary composition.
U.S. Pat. No. 6,143,324 also discloses a free-flowing, directly-compressible starch. In this case, an aqueous slurry of native starch is first heated to about 62° C. in order to cause partial swelling of the starch granules without causing disruption of the starch granules. The slurry is then cooled and spray-dried to yield a free-flowing powder. The '324 process eliminates the step of forming an intermediate starch paste; however, protracted heating and cooling steps are still involved. The product so formed has a ratio of non-swollen birefringent granules (intact native starch) to swollen non-birefringent granules (gelatinized starch) of 1:5 to 5:1. U.S. Pat. No. 6,455,069 dislcoses tabletting compositions comprising the '324 free-flowing, directly-compressible starch and at least one other excipient.
U.S. Pat. No. 6,184,213 discloses a diluent and disintegrating starch composition, which is comprised of amylose-rich starch granules in a pre-gelatinized starch matrix. This composition is prepared by mixing conventional and amylose-rich native starch slurries, each about 35% by weight in water, heating and drying the resultant mixture at about 100° C. to obtain a paste, and, finally, grinding said paste. Some of the native starch is gelatinized during the heating and drying process to yield the gelatinized starch matrix.
U.S. Pat. No. 6,322,818 discloses the preparation of agglomerated, spherical particles by coating starch seeds with successive layers of starch granules and pre-gelatinized starch. In this process, solid starch seeds are “fluidized” in a fluid bed apparatus, and a slurry of pre-gelatinized starch and native starch granules is then layered or coated onto the seeds such that agglomerates with spherical shapes are obtained. The spherical particles of this disclosure are used as carrier materials. Active pharmaceutical ingredients and excipients are coated or “loaded” onto these carrier particles.
Japanese patent application JP 56-28606 relates to the preparation of granular potato starch. It discloses a process wherein potato starch is charged in a fluidizing granulator, and a solution of gelatinized potato starch is sprayed as a binder. The fluidized potato starch agglomerates and grows surrounding the binder-starch nucleus to obtain fine granular potato starch with an average particle size of 150 to 1,000 micrometers. The process disclosed relies on the preparation of an intermediate gelatinized potato starch solution by heating a dispersion of potato starch in water at 80° C.
Pre-compacted starch powders for use as binders and/or disintegrants in the manufacture of tablets by direct compression and as fillers for formulations supplied in hard gelatin capsules are described in U.S. Pat. Nos. 3,622,677 and 4,072,535. Pre-compacted starch powder is obtained by subjecting a non-gelatinized granular starch to physical compaction between steel rollers with the possible input of thermal energy. The pre-compacted starch powder shows the presence of sharp birefringent granules and non-birefringent fragments of granules as well as some aggregates of granules and fragments. After the compaction, the starch is ground and sieved to yield a free-flowing powder. Tablets and capsules comprising the '677 and '535 starches have the tendency to disintegrate more slowly in a neutral aqueous medium than in a low pH medium (e.g. pH 1.2).